Freeze start operation in a fuel cell with a blocked anode cell

Abstract

Methods for starting a fuel cell system are provided. In one embodiment, the method includes providing hydrogen to an inlet of an anode of the fuel cell pressurizing the anode to a pressure; determining whether a blocked cell condition exists; if a blocked cell condition exists, if no blocked cell condition exists, initiating a normal start sequence, alternately reducing the pressure of the anode and increasing the pressure of the anode until an exit condition exists, the exit condition selected from a voltage of the fuel cell being stable, or a temperature of the fuel cell being greater than about 0° C., or both, and when the exit condition exists, initiating the normal start sequence.

What is claimed is: 
     
       1. A method for starting a fuel cell, the method comprising:
 providing hydrogen to an inlet of an anode of the fuel cell to pressurize the anode to a pressure; 
 measuring a cell temperature and a cell voltage of the fuel cell; 
 determining from the cell temperature and the cell voltage whether a blocked cell condition exists, wherein the blocked cell condition comprises a blocked anode channel of the fuel cell having an ice blockage, and wherein the blocked cell condition exists when the cell voltage is negative and the cell temperature is below 0° C.; 
 if no blocked cell condition exists, initiating a normal start sequence; 
 if a blocked cell condition exists, alternately and in any order:
 reducing the pressure of the anode to discharge from the blocked anode channel any nitrogen or other non-hydrogen gas that remains in the blocked anode channel after the hydrogen has been consumed in the blocked anode channel by operation of the fuel cell; and 
 increasing the pressure of the anode to compress hydrogen into the blocked anode channel, 
 
 until an exit condition exists that ensures the ice blockage in the blocked anode channel has melted, wherein the exit condition exists when the cell voltage is stable and the cell temperature is greater than 0° C.; and 
 when the exit condition exists, initiating the normal start sequence. 
 
     
     
       2. The method of  claim 1 , further comprising reducing a load on the fuel cell while reducing the pressure of the anode, or while increasing the pressure of the anode, or both. 
     
     
       3. The method of  claim 1 , wherein the pressure of the anode is reduced in less than 10 seconds and the pressure of the anode is increased in less than 5 seconds. 
     
     
       4. The method of  claim 1 , wherein increasing the pressure of the anode comprises increasing an anode pressure set point. 
     
     
       5. The method of  claim 1 , wherein increasing the pressure of the anode comprises opening a hydrogen supply valve. 
     
     
       6. The method of  claim 1 , further comprising heating the fuel cell while reducing the pressure of the anode, or while increasing the pressure of the anode, or both. 
     
     
       7. The method of  claim 6 , wherein the fuel cell is heated with an auxiliary heating source. 
     
     
       8. The method of  claim 1 , further comprising monitoring the voltage of the fuel cell to determine whether the voltage of the fuel cell is stable. 
     
     
       9. The method of  claim 1 , wherein the pressure of the anode is reduced before the pressure of the anode is increased. 
     
     
       10. The method of  claim 1 , wherein the pressure of the anode is increased before the pressure of the anode is reduced. 
     
     
       11. A method for starting a fuel cell having an anode with a blocked anode channel that contains an ice blockage, the method comprising:
 alternately, and in any order:
 increasing a pressure of the anode to compress hydrogen into the blocked anode channel; and 
 decreasing the pressure of the anode to discharge from the blocked anode channel any nitrogen or other non-hydrogen gas that remains in the blocked anode channel after the hydrogen has been consumed in the blocked anode channel by operation of the fuel cell, 
 
 until an exit condition exists that ensures the ice blockage in the blocked anode channel has melted, wherein the exit condition exists when a cell voltage of the fuel cell is stable and a cell temperature of the fuel cell is greater than 0° C.; and 
 initiating a normal start sequence when the exit condition exists. 
 
     
     
       12. The method of  claim 11 , further comprising reducing a load on the fuel cell while reducing the pressure of the anode, or while increasing the pressure of the anode, or both. 
     
     
       13. The method of  claim 11 , further comprising opening an anode discharge valve while reducing the pressure of the anode. 
     
     
       14. The method of  claim 11 , wherein the pressure of the anode is reduced in less than 10 seconds and the pressure of the anode is increased in less than 5 seconds. 
     
     
       15. The method of  claim 11 , wherein increasing the pressure of the anode comprises opening a hydrogen supply valve. 
     
     
       16. The method of  claim 11 , further comprising heating the fuel cell while reducing the pressure of the anode, or while increasing the pressure of the anode, or both. 
     
     
       17. The method of  claim 11 , further comprising monitoring the voltage of the fuel cell to determine whether the voltage of the fuel cell is stable.